Sound-absorbing method and material



Feb. 12, 1924.

J, MAzER SOUND ABSORBING` METHOD AND MATERIAL 2 Sheets-Sheet 1 Filed June 27, 1918- FIG'. 1 FIG- FIG. 4

Patented Feb. 12, 1924.

PATENT OFFICE.

JACOB MAZER, F PITTSBURGH. PENNSYLVANIA.

SOUND-ABSORBING METHOD AND MATERIAL.

Application led June 27, 191B. SerialNo. 242,272.

To (I/ l1li/mmV if may conce/'11,.'

Be it known that l, JAoor. MAZER, a citizen of the United States, and resident of Pittsburgh, in the county of AUlcglicny and State of Pennsylvania, have invented a new and useful Improvement in So\1ml-.\l so1bing Methods and Material; and I do hereby declare the following t0 be a full, clear. and exact description thereof.

My invention relates to an improved sound-absorbing material.

The object of my invention is to provide a sound-absorbing material for halls. auditoriums or other enclosures and adapted to be used. without change of structure, as a surface material for walls` ceilings and the like, or, between walls` ceilings and floors and the like. l

For the firstmeutioned purpose, this improved souml-absorbing material would be applied on the walls, ceilings and other boundary surfaces o t rooms in such quantities and in such position as might be found necessary to correct the defective conditions for hearing in an auditorium or other enclosure, or would be applied during the construction of an auditorium or other enclosure., after determining by proper computations, the position and amount of the said sound absorbing mate-rial required.

In addition to improving the acoustics within the room, this material greatly rcduces the amount of sound transmitted from extraneous sources into the room.

For the second-mentioned purpose, namely the application of the improved soundabsorbing material between the walls, ceil ings and floors and the like, it would .serve only to prevent the transmission of sounds through the walls, ceilings, floors and the like. l

My invention aims particularly to provide sound absorbing material having predetermined and controllable sound-modifying effect which may be selected and con' trolled, and )vhich is producedby surface apertures which are in free communication with the room or other space where the acoustics are to be controlled. The surface apertures may be formed. in the material in advance of its installation, or may be formed in the material after the`materal has been placed in position. This general. aspect of my invention is capable of being put to use with a great variety of substances and with many different ar 'angements of apertures, some of which are described below.

This invention differs from my previous Patent No. 1.172,879 in that the improved construction herein provided for, is com sed of solid or at least comparatively rigif ma ferial, as distinguished from loose substances in the nature of felt, and has a series of sur face apertures which-has a uniform soundabsorbing capacity per unit of area. The individual apertures, in some embodiments of' my invention, may be regularly shaped, uniform in size, and of much greater length than width. In other embodiments, as for example in those shown in Figs. 9 and l() of the accompanying drawing, the individual apertures are of different sizes and are distributed 'more or less irregularly, but always in such a manner as to give a definite and predetermined sound-modifying effect per square foot, square yard, or other unit of exposed surface. This provision of uniform sound-absorption per unit of area makes it possible to calculate accurately the amount and precise structure of the material needed for any particular case, and to know in advance, and independently of the skill of the workmen, just what result will be produced by any particular element constructed according to my invention.

Itis commonly known by students of the. behavior of sound that absorption of part of the energy of the sound takes place at each'itnpaet of the sound wave with a surface and that the sound is reflected from the surface at an angle equal to the incident angle. All other factors remaining equal, an increase in the lrate of absorption of a sound is brought about by decreasinfr. the distance between the surfaces from which it is repeatedly deflected. Therefore by pro-` viding long narrow apertures, the length of which is considerably greater than the width of the openings, I have a construction that is highly sound-absorbing, since it will cause a rapid decay of the sound even though the materials of which it is composed and which form the walls of the apertures, are not themselves high-ly sound-absorbing.

It follows also that if the apertures just described, communicate with other openings or apertures within the sound-absorbing material, the process of sound absorption will be increased in such manner that the opportunities are still more remote for a sound to emerge at the surface Where 1t entered the aperture.

I have found that any material can be made to absorb a large percentage of sound if its construction is such that when the sound strikes it a great number of impacts must take place within a very short period of time. This is because, as previously nien. tioned, a definite absorption of sound takes place at each impact? Fig. 1 shows onetype of the improved acoustic material; F ig. 2 shows, an enlarged section of one of the apertures in said material; Figs. 3 and 3a show enlarged sec' tions ot' apertures in two varieties of another form of the material; Fig. 4 shows still another form of the material; Figs. :'i to l2 show still other forms ot' the device.

In the form of m invention illustrated in Fig.' 1, the material is shown to consist of a block l of originally plastic material and provided with a number of apertures 2 penetrating into the block from one face, and also showing a number of apertures 3 penetrating in from another f ace.

Fig. 2 of the accompanying drawings shows an enlarged view of a section of one of the multitude or series of tube-like apertures with which the material shown in Fig. l is provided. The particular section shown has width of aperture larger than that which would be usually provided for an aperture of such comparatively short length and illustrates approximately what would take place during the course of the decay of a sound under the poorest conditions of our construction. Assuming that a soundE wave 5" strikes the face of my material at any angle X, the course of propagation is designated by the arrow points, and impacts against the side of the aperture and consequent absorp-A tion take place at A', A2, A3, etc.

It will be seen that the sound entering the aperture will be partially absorbed at each successive impact. It' total absorption takes place somewhere about the point A20 no sound will emerge from the aperture.

It will also be seen that by changing the width, length or number of apertures entering a given structural element can increase or decrease tlre sound-absorbing efficiency of the material.

It must not be supposed that soundabsorbing material of very high soundabsorbing capacity is necessarily better than material of lower sound-absorbing capacity. It frequently happens in practice, that a room of large surface area. requires only moderate sound-modification. in which case the absorbing capacity ot' the material must be reduced accordingly. Even the smallest and fewest apertures have some absorbing power, and an almost infinite range oi controlis therefore possible through the use of surface' apertures of various sizes and various distributions.

Fig. 3 Ashows an enlarged section 4 with the apertures 5 of another forni of the inaterial, said apertures containing felt 6, or other highly sound-absorbing material, in all or part of the aperture.

Fig. 3a shows a construction similar to Fig. 3 with the difference that the apertures 5a containing the felt or like material 6 are closer together than the apertures 5 of Fig. 3.

Fig. 4 shows still another form 7 of the material, behind the surface ot' which is felt or other highly sound-absorbing inaterial 8, communicating with apertures 9 extending to one or more of the surfaces ol: said first-mentioned material.

Figs. 5 and 6 show the material toi-ined in blocks l() and l1 having in their interiors open spaces l2 and 13 communicating with the apertures 14 and ,15, respectively.

It is understood that these apertures may vary greatly in width and may he arranged to present on the face of the material vaiious designs to form a part of the decorative scheme of a room.

It will be understood that the principles of my invention may be carried out by forming the sound-absorbing apertures not. only in blocks` sheets oi' other structural elements, but also in the surface oi an already erected wall or ceiling, Thus a wall or ceiling may be coated with plaster in the usual way, and sharp points may be pressed against the plaster b v means ol a roller or other instrument; and such sharp points may make the necessary apertures either by mcclianically puncturing the surface or by the ehemical action of an acid or other reagent applied by the sharp points or otherwise.

It is well-known that mixtures of plaster of high porosity do not produce as much reverberation in a room as the harder nonporous forms. However. the number of cases of detective conditions tor hearing in rooms covered with the more porous forms o f plasters. demonstrate that they do not 4provide sufiicient absorption for good acoustics.

In practice the formation of my long and narrow.apertures in ordinary forms otl plaster -inst before the plaster has t, is a cheap and practical way of obtaining the desired result and my invention covers just such eondition. The apertures may. if desired` be arranged in various ornamental designs.

The materials described are preferably composed of plastic combina-tions of substances which are capable of being molded to various shapes,l and which will take a final set and harden so as to be of substantial structural use. Such materials are gypsum, sand and cement mixtures, sand and linie mixtures and the like, but the construction is not` of course. confined to these materials as almost any material constructed in the manner described would be highly sound ab sorbin In 4ig. 7 is illustrated a further modification of my improved acoustic material. In this case the material may be in the form of a block 1G of plaster or the like which is kert'ed or slotted as at 1i' to form longitudinal grooves. These grooves have the same sound deadening effect on the sound waves as the pertorations in the above described constructions have.

Again in Fig. S is illustrated a further modification of the improved acoustic material which may consist of units or blocks of corrugated flexible material, suoli as paper, fiber-board or the like, which is bent into convolutions 18 thus presenting at the outer face grooves or passages such as 19 similar to the grooves 17 in the unit illustrated in Fig. 7. This corrugated material may have at the rear or one face, a backing strip or sheet 20 by which the material is held together as a unitary structure. Y

In Fig. 9 is illustrated a still further modification in which layers or strips 21 ot suitable material, such as paper, fiber-board, cloth` felt or the like.. may be laid together and secured to a backing member 22. The securing means may be cement. or other suitable t'astening means. The edges 23 of these strips or layers will necessarily present spaces or grooves between them of greater or less width according to the character o the. material used or the smoothness of the surfaces thereof. and these interstices between the layerslwill present sound deadening cavities similar to those shown in the forms illustrated in Figs. 7 and 8.

ln Fig. 10 is shown a further modification, the layers or strips 24 being suitably secured to the backing 25 may be still more separated b v means of particles 26 of fiber, sand or other suitable finely divided material, which will cause greater spacing apart of the layers or strips 211 than would result from the construction shown in Fig. 9.

It will be observed that the exposed'surf faces shown in Figs. 9 and 10, particularly in Fig. .10, are not perfectly smooth, but are somewhat irregular. Such unevenness is often desired b v architects and decorators, and may readily be provided by my present materials. without destroying the definite absorbing power perk unit area described above.

In Fig. 11 the strips or layers 27 may be positively spaced apart in uniform manner by spacing strips 28, whereby interstices or sound absorbing apertures will be formed between the strips. Finally in Fig. 12 is illustrated a form of material in which the strips or layers`29 may be 4spaced apart by short strips or blocks 30 which do not cxtend fully across the width of the strips 29, and which may be staggered in position, as illustrated to form more or less irregular openings or interstices for the absorption of the sound. In this case it will be noted that,the openings or interstices extending inward from the. edges of the adjacent strips 29 will communicate with cross openings, such tor example,` as 31 between the ends ot the short spacing strips, and consequently the interstiees extending inwardly from the edges ot' the material may also communicate one with the other.

The material also may be formed into units of various sizes `and of measurable sound-absorbing efficiency.

lhile I have herein described particular embodiments ot' my invention, it is understood that the same may be altered in many details in relative arrangement of parts, in the manner and method of manipulating the acoustical elements and in the manner of applying and securing the same to or Within the walls, ceilings or other surfaces, Within the scope of the patent claims.

What T claim is:

1. The method of establishing predeter-v mined accustic conditions for an enclosure that comprises providing in connection with a boundary surface thereof a setuid-absorbing material having apertures opening at the surface exposed to the sound waves, said apertures being ot such number. dimensions and arrangement as to produce definite and predetermined soiindabsorbing capacity per unit area of the said exposed surface.

2. Sound-modifying material comprising a body having apertures mechanically and definitely vformed therein and communicating with a normally exposed surface of said body, the said apertures being sufficiently numerous to have substantial sound-modifying effect, and said. surface having definite and predetermined sound-absorbing capacity per unit area of said surface.

3. Sound-modifying material comprising a body having apertures penetrating said body from a normally exposed surface thereof, said apertures being definite in shape and sufficiently' numerous to have substantial and predetermined sound-modifying eiiect, and cach of the said apertures being ot materially greater length than width.

4. Souiul-n'iodifying material comprising a non-refractory body adapted for use on the surface of walls, ceilings or other portions of' an auditorium or enclosure, and having a series ot similar sound absorbing apertures penetrating said body trom a normally exposed surtace thereof, said apertures being of regular shape and sufiiciently numerous to have substantial and predetermined soumhmoditying effect, and each of the said apertures being" of inat-erialb' greater length than width.

5. Sound-inoditying material comprising a non-refractory body adapted for ilse on the surface ol' iralls` ceilings or other portions ot an auditorium or other enclosure, and having a plurality ot' similar sound-absorbing apertures penetrating said body from a normally exposed surface thereof, said apertures being ot' regular sliapi` and sutliciently numerous to have substantial and predetermined sound-moditying etr'ect, and nach of the said apertures being ot materiallyY greater length than width.

G. A sound-moditying body having an internal cavity and haring a plurality of similar apertures sufiicieiitly numerous to have substantial and predetermined sound-moditying eli'ect, the said apertures communicating, when the said material is in use, with the said internal cavity and with a normally exposed surface of said body.

7. A sound-absorbing body having an internal cavity and having a plurality of regular and similar apertures suiiciently numerous to have substantial and predetermined sound-modifying eect, said apertures pene trating from a plurality of `surfaces of said y body, and communicating Witlithe said internal cavity, each of the said apertures beiiig of materially greater length than Width and being of substantially uniform cross section.

S. Sound-modifying material comprising a body adapted for use on the surface i' posed surface of said material into said inaterial, certain of said apertures containing lfibrous sound-absorbing material, and sai and predetermined sound absorbing capacity per una area ot' said surface, and said material being constructed in units ofl various sizes and shapes of predetermined soundabsorbing efficiency and ready for application without the necessity of alteration.

10. The method of establishing predetermined acoustics for an enclosure that com prises the steps of providing the enclosure with -surface material capable of receiving apertures, and then forming in the said material apertures communicating With the eX- posed surface of said material, the said apertures producing definite and predetermined soiiiid-absorbiiig capacity in said material. In testimony whereof, I the said JACOB MAZER, have hereunto set my hand.

JACOB MAZER.

Witnesses:

JOHN F. WILL, S. F. ARMSTRONG. 

